The present invention relates to metal laminate gaskets with thickness adjusting mechanisms for internal combustion engines, which can provide the same grades with different thicknesses.
In the internal combustion engines, the cylinder heads and cylinder blocks are mass-produced in the same methods and conditions. However, when the cylinder head and the cylinder block are assembled together without a gasket therebetween, slight deviations or changes appear in the gap between the cylinder head and the cylinder block. Namely, the gap between the cylinder head and the cylinder block is different individually.
In order to provide the engines with the same qualities and characteristics, it is required to form the same surface pressures on the gasket when the engines are assembled. Thus, in case the gap between the cylinder head and the cylinder block is different, a gasket with different thickness is installed between the cylinder head and the cylinder block. In this case, it is required in each gasket that a difference in thicknesses between a sealing portion around a cylinder bore and a portion away from the sealing portion is made constant, while the thickness of the gasket is changed.
In case a gasket is formed of a first metal plate with a turned portion, i.e. curved portion and flange, and at least one second metal plate laminating with the first plate without overlapping the flange, which is known in the art, if the thicknesses of the first and second metal plates are changed, the above requirements can be satisfied. However, since the first plate is turned at the curved portion, the first plate must have the minimum thickness. Otherwise, when the first plate is turned at the curved portion, the curved portion may have a crack. Thus, it is not practical to form different grade gaskets by changing the thickness of the metal plate with the curved portion.
If an additional plate laminating with the flange and the second plate is used together with the first and second metal plates, in case the thickness of the additional plate is adjusted, the above requirements can be satisfied. However, since the gasket has three metal plates, the minimum thickness of the gasket becomes relatively thick. Thus, this structure is not suitable for a thin gasket.
In addition to the above gaskets, U.S. Pat. No. 5,435,575 discloses a gasket formed of three metal plates with a seal ring, which can securely seal around the gasket. Also, U.S. Pat. No. 5,141,237 discloses a gasket with a plate information device, which can identify the gaskets with different types. The prior art patents work properly as intended, but the improvement of the gasket is still required.
In view of the conventional gaskets, the present invention has been made, and an object of the invention is to provide a metal laminate gasket with a thickness adjusting mechanism to provide different grade gaskets easily.
Another object of the invention is to provide a metal laminate gasket as stated above, wherein the thickness of the gasket can be changed easily without causing a damage to the gasket.
A further object of the invention is to provide a metal laminate gasket as stated above, which is made relatively thin.
A still further object of the invention is to provide a metal laminate gasket as stated above, wherein the gaskets with different thicknesses can be identified easily.
Further objects and advantages of the invention will be apparent from the following description of the invention.
A metal laminate gasket of the invention is used for an internal combustion engine. Especially, the gasket is suitable for a cylinder head gasket for sealing around a cylinder bore.
The gasket is basically formed of a first metal plate, and one plate combination selected from a plurality of plate combinations laminated with the first metal plate. The first metal plate includes a base portion extending substantially throughout an entire area to be sealed, a curved portion extending from the base portion to define a first hole therein corresponding to the cylinder bore to be sealed, and a flange extending from the curved portion in a direction away from the first hole.
Each plate combination includes an annular shim disposed between the flange and the base portion, and a second metal plate having a second hole and disposed under the base portion without laminating the annular shim and the flange. The thickness of the second metal plate is greater than the thickness of the annular shim and less than the total thicknesses of the annular shim and the flange. Thus, when the gasket is tightened, the surface pressure on the flange is greater than that formed on the second metal plate outside the flange to securely seal around the first hole. Also, the difference of the surface pressures formed on the flange and the second metal plate can be precisely set by adjusting the thicknesses of the annular shim and the second metal plate.
Each plate combination has different thicknesses in the annular shim and the second metal plate while keeping a difference in thicknesses between the annular shim and the second metal plate constant. Namely, the annular shim and the second metal plate in one plate combination are different in thicknesses from the annular shim and the second metal plate in another plate combination, respectively. However, the difference of the thicknesses between the annular shim and the second metal plate is constant in one and another plate combinations. Thus, the gaskets having the same grades with different thicknesses are formed easily by changing the plate combinations.
In installing the gasket between the cylinder head and the cylinder block, at first, the cylinder head and the cylinder block are laminated without a gasket, and a gap or clearance between the cylinder head and the cylinder block is measured. Then, the cylinder head is removed from the cylinder block, and the gasket with an appropriate size is selected based on the size of the gap and is situated on the cylinder block. Then, the cylinder head is once again placed on the cylinder block with the gasket therebetween, and the cylinder head and the cylinder block are tightened.
In this respect, a gasket with a predetermined thickness is installed in a predetermined range of a gap between the cylinder head and the cylinder block without the gasket. Namely, if the gap is large, a thick gasket is installed between the cylinder head and the cylinder block. Therefore, the engines with the same qualities and characteristics can be formed regardless of the gap between the cylinder head and the cylinder block.
In the invention, since the thicknesses of the annular shim and the second metal plate are changed in changing the thickness of the gasket without changing the thickness of the first metal plate, the quality of the gasket can be maintained at the same level. Namely, even if the thickness of the gasket is reduced, since the thickness of the first metal plate is not changed and is constant, which is appropriate to form the curved portion, there is no possibility of causing the damage at the curved portion.
In this respect, if the thickness of the first metal plate is changed in changing the thickness of the gasket, when the first metal plate is bent at the curved portion, the cuved portion may have a crack depending on the quality of the first metal plate and the thickness thereof. In the invention, since the thickness of the first metal plate is not changed in changing the thickness of the gasket, the first metal plate can be surely bent at the curved portion, so that the quality of the gasket is kept constant.
In the invention, each of the plate combinations has a sign for indicating the plate combination. The signs are different depending on the differences of the thickness of the plate combinations. Each sign of the plate combination includes a projection with an indentation formed at one of the annular shim and the second plate, and a dent for receiving the projection formed at the other of the annular shim and the second plate.
In the invention, since the signs are formed on the gaskets, the gaskets with different thicknesses can be identified easily. Also, since the sign is formed of the projection and the dent, the sign does not affect the sealing ability of the gasket.
Preferably, the first metal plate includes a first bead around the first hole, which is located above and extends toward the flange, and the annular shim includes a second bead located on the flange and extending toward the base portion. The cylinder bore can be securely sealed by the beads.